Author Topic: Fluke 289 schematic or part identification help  (Read 4776 times)

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Offline SonicskaterTopic starter

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Fluke 289 schematic or part identification help
« on: May 26, 2018, 06:55:06 pm »
Does any one have a schematic for a Fluke 289 or willing to open theirs to let me know what a couple components are?  I have a unit that the previous owner tried to open by prying the case and they took out C2 Q1 R1.  The pads are still in place so I can solder on replacements.  The meter works so not sure what part of the circuit this is for but they are located between the two middle meter lead sockets.
« Last Edit: May 26, 2018, 07:16:23 pm by Sonicskater »
 

Offline coromonadalix

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Re: Fluke 289 schematic or part identification help
« Reply #1 on: May 26, 2018, 11:41:01 pm »
there's no service manual available if i recall correctly,  you have some thread here, maybe on some photos you can see a few parts, maybe they are for input protections  since you say your meter seems to work ??
 

Offline SonicskaterTopic starter

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Re: Fluke 289 schematic or part identification help
« Reply #2 on: May 26, 2018, 11:58:30 pm »
Thanks.  I’ve zoomed in on any pictures I could find with no luck.  It’s odd but the meter works fine, although I haven’t tried every feature but the common ones I would use all work.
 

Offline retiredcaps

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Re: Fluke 289 schematic or part identification help
« Reply #3 on: May 27, 2018, 03:16:56 am »
R1 looks like 104?, Q1 looks like 1AH?, don't know what C2 value is.

See post

https://www.eevblog.com/forum/reviews/fluke-287-dmm-teardown-and-photos/msg52680/#msg52680
 
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Offline ModemHead

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Re: Fluke 289 schematic or part identification help
« Reply #4 on: May 27, 2018, 03:03:07 pm »
This meter uses optical detection for when plugs are inserted into the current jacks.  The components in question are part the photo-transistor detector circuit for the mA jack directly on the other side of the board.

Maybe the jack has some crud in it that causes the lead alarm to go off, and the previous owner removed the components to silence it.  Just a guess, as I've done exactly this to a 27-II model with jacks that were damaged by solvent.

The transistor "1AM" is a MMBT3904 general-purpose NPN transistor. The "104" resistor is 100K.  I cannot get an in-circuit read on the cap, as I found a voltage differential on it due to the super-cap.  Probably just a filter to prevent false triggering due to ambient IR?
 
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Offline Chris56000

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Re: Fluke 289 schematic or part identification help
« Reply #5 on: May 27, 2018, 04:28:12 pm »
Hi!

I use a 287 at work, but my manager'd be down on me like a ton of bricks if I took mine to bits without a good cause, but from examination of C2 in the piccy provided in the linked thread, I'd venture to suggest 100n 50V 0805 as a reasonable starting-point!

Chris Williams
It's an enigma that's what it is!! This thing's not fixed because it doesn't want to be fixed!!
 

Offline SonicskaterTopic starter

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Re: Fluke 289 schematic or part identification help
« Reply #6 on: May 27, 2018, 06:18:55 pm »
Thanks everyone for the help!  Appreciate it.
 

Offline retiredcaps

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Re: Fluke 289 schematic or part identification help
« Reply #7 on: May 28, 2018, 04:13:29 am »
Thanks everyone for the help!  Appreciate it.
Let us know if replacing these parts makes it work.
 

Offline retiredcaps

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Re: Fluke 289 schematic or part identification help
« Reply #8 on: May 28, 2018, 04:14:25 am »
The transistor "1AM" is a MMBT3904 general-purpose NPN transistor.
I couldn't quite make out the last letter.
 

Offline SonicskaterTopic starter

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Re: Fluke 289 schematic or part identification help
« Reply #9 on: May 28, 2018, 04:56:46 pm »
Thanks everyone for the help!  Appreciate it.
Let us know if replacing these parts makes it work.
Will do, I had to order the parts but hope to have them by the end of the week.
 

Offline SonicskaterTopic starter

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Re: Fluke 289 schematic or part identification help
« Reply #10 on: June 10, 2018, 07:11:04 pm »
Parts took longer to get here so I just now got it put back together.  I found the capacitor in the case and it measures at 500nf.  With the other parts now installed it works perfectly.  Thanks again for all the help!
 


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